I. Field of the Present Invention
The present invention relates generally to a housing for an electrical starter motor, and more particularly, to particular construction of a bearing support for rotatably supporting a rotor shaft within the motor housing.
II. Description of the Prior Art
As is well known, electric motors such as starter motors for internal combustion engines include a rotor shaft rotatably mounted within the motor housing. A rotor winding is secured to the rotor shaft for rotation therewith which is coaxially arranged within a set of stator windings. While the interaction of the electromagnetic forces between the stator windings and rotor windings causes rotation of the rotor shaft, it is necessary to support the shaft in a manner which maintains the alignment between the stator winding and the rotor winding. Thus, bearings are provided in the starter motor housing for rotatably supporting the shaft.
Quite often the bearing assemblies are ball or roller bearing assemblies which require lubrication to minimize resistance to rotation, and to prolong the life of the bearing parts. The bearing support structure is often provided with fluid passageways to direct a supply of lubricant to the bearing. Thus, construction of the bearing support to include such lubricating means increases the cost and complexity of the bearing housing. In addition, it is necessary to protect the electrical components of the starter motor from environmental conditions and debris, and the housing is, therefore, constructed so as to completely enclose the windings and other electrical components within the housing. However, the space intermediate the rollers between the inner and outer race of the bearing permit dust and other environmental debris to enter within the housing and build up upon the internal parts of the starter motor. Thus, the axially outermost end of the bearing may be provided with a seal to prevent the introduction of foreign matter through the bearing and into the interior of the motor housing. However, such placement of the seal further complicates or restricts placement of lubricant passages which provide lubricant to the bearing. Moreover, such an arrangement does not prevent lubricant from entering the interior of the starter motor housing and contaminating the components therein.
While self-lubricating bearing materials can be used to eliminate the need for continuous lubrication of the bearing, the above described seal arrangement fails to protect the starter motor components from particulate debris which can result from wear on the self-lubricating material. In addition, disassembly of the housing or modified construction of the housing would be necessary to provide supplemental lubrication to the bearing.